Braking control systems are well known in the prior art and have been designed for vehicles from small passenger vehicles to large trucks. A frequent object of such systems is to optimize braking effectiveness and vehicle control. Another object is to control the braking effort contributed by each braking site to provide balanced and proportional braking. Such systems find particularly useful application on large, articulated trucks. Control systems for proportionally distributing braking effort include systems operated as a function of vehicle acceleration and various forces and as a function of vehicle driver demand.
Typical of the latter type of control systems are those disclosed by U.S. Pat. Nos. 4,768,840; 4,804,234; and 4,804,237 to Gee and Sullivan. The first cited patent discloses a vehicle braking control system that senses the magnitude of driver demand for braking effort and causes each of the braking sites to exert a braking force that is dependent on the value of the demand and independent of load under conditions of relatively low braking effort demand and causes each of the braking sites to exert a braking force that is directly related to the value of the demand and to the load at the braking site under conditions of relatively high braking effort demand.
The second cited U.S. Pat. No. 4,804,234 discloses a vehicle braking control system that senses the magnitude of driver demand for braking effort, that determines the ratio of the horizontal to vertical force at the fifth wheel/king pin connection of the vehicle, and that senses vehicle acceleration. The braking control system, when the vehicle is under conditions of relatively low braking effort demand, causes each of the braking sites to exert a braking force that is dependent on the value of the demand and independent of load. When the vehicle is under conditions of relatively high braking effort demand, the braking control system causes each of the braking sites to exert a braking force that is directly related to the vehicle acceleration, to the value of the demand, and to the load at the braking site.
The third cited U.S. Pat. No. 4,804,237 discloses a vehicle braking control system that senses the amounts of horizontal and vertical forces at the fifth wheel/king pin connection of the vehicle, that senses vehicle acceleration, and that senses the magnitude of driver demand for braking effort. The trailer mass is estimated from sensed values of horizontal forces acting at the fifth wheel/king pin connection of the vehicle during nonbraking acceleration, and the force applied to each trailer brake is sensed and compared with reference levels to estimate an average characteristic for the trailer brakes, If driver demand is less than a reference level, tractor and trailer brakes are applied such that the average value of a selected parameter indicative of trailer brake wear is related in a predetermined manner to the average value of the parameter indicative of tractor brake wear.
While each of these braking systems functions with a certain degree of efficiency, none discloses the advantages of the method and apparatus for equalizing the brake wear of a braking vehicle of the present invention as is hereinafter more fully described.